ACTIVATION METHOD USING MODIFYING AGENT

Abstract

The present invention relates to a method of activating an organic coating to enhance adhesion of the coating to a further coating and/or to other entities comprising applying a solvent and a surface chemistry and/or surface topography modifying agent to the organic coating.

The invention also relates to a coated substrate having an activated coating, wherein the adhesion of the coating to a further coating and/or other entities has been enhanced by application of a solvent and a surface chemistry and/or surface topography modifying agent to the coating.

The invention further relates to an activation treatment for an organic coating to enhance adhesion of the coating to a further coating and/or to other entities comprising a solvent and a surface chemistry and/or surface topography modifying agent and a method for the preparation of the activation treatment.

Claims

1. A method, comprising: applying a solvent and a surface modifying agent to a surface of an aged or inert organic coating to surface hydrolyze the surface of the aged or inert organic coating.

2. The method of claim 1, wherein the surface modifying agent is an acid.

3. The method of claim 2, wherein the acid is an organic acid.

4. The method of claim 3, wherein the organic acid is selected from the group consisting of formic acid, acetic acid, benzoic acid, propanoic acid, malonic acid, oxalic acid, and combination(s) thereof.

5. The method of claim 2, wherein the acid is an inorganic acid.

6. The method of claim 5, wherein the inorganic acid is phosphoric acid.

7. The method of claim 1, wherein the modifying agent is present in a composition with the solvent when applying the solvent and the surface modifying agent to the surface, wherein the modifying agent is present in the composition in an amount of about 0.001% to about 20% based on the total weight of the combination of solvent and agent.

8. The method of claim 1, wherein the solvent is selected from the group consisting of an organic solvent, water, and combination(s) thereof.

9. The method of claim 8, wherein the solvent is an organic solvent selected from the group consisting of an ester, a ketone, an alcohol, an ether, an amide, an aromatic, a halogenated solvent, and combination(s) thereof.

10. The method of claim 9, wherein the organic solvent is an ester selected from the group consisting of ethyl acetate, ethoxyethyl acetate, isopropyl acetate, tertiary butyl acetate, and combination(s) thereof.

11. The method of claim 10, wherein the ester is ethyl acetate.

12. The method of claim 8, wherein the solvent is selected from the group consisting of tetrahydrofuran, N-methyl pyrrolidinone, water, and combination(s) thereof.

13. The method of claim 12, wherein the solvent is N-methyl pyrrolidinone.

14. The method of claim 8, wherein the solvent is a combination of N-methyl pyrrolidinone: ethyl acetate.

15. The method of claim 1, wherein the aged or inert organic coating is selected from the group consisting of a polyurethane, an epoxy, a polyester, a polycarbonate, an acrylic coating, and combination(s) thereof.

16. A coated substrate, comprising: a surface hydrolyzed organic coating disposed on a substrate, the surface hydrolyzed organic coating formed by application of a solvent and a surface modifying agent to an aged or inert organic coating; and a further coating disposed on the surface hydrolyzed organic coating, the further coating selected from the group consisting of an adhesive, a sealant, a pin hole filler, a decal, a logo, and combination(s) thereof.

17. The coated substrate of claim 16, wherein the substrate is selected from the group consisting of a metal, a composite, a plastic, an elastomer, glass, wood, a fabric, and combination(s) thereof.

18. The coated substrate of claim 16, wherein the surface modifying agent is an organic acid selected from the group consisting of formic acid, acetic acid, benzoic acid, propanoic acid, malonic acid, oxalic acid, and combination(s) thereof.

19. The coated substrate of claim 18, wherein the aged or inert organic coating is selected from the group consisting of a polyurethane, an epoxy, a polyester, a polycarbonate, an acrylic coating, and combination(s) thereof.

20. The coated substrate of claim 18, wherein the solvent is selected from the group consisting of N-methyl pyrrolidinone, ethyl acetate, and combination(s) thereof.

Description

DETAILED DESCRIPTION OF THE DRAWINGS

[0149] In the Examples, reference will be made to the accompanying drawings in which:

[0150] FIG. 1 is photographs showing the impact on different metalalkoxide modifying agents and concentration on inter-coat adhesion. (Base coat: DHS BAC70846, C2. Base cure condition: 16 h, 120 F, 8% RH. Over-coat: BAC50103, C. Over-coat cure: 4 days, 120 F, 10% RH.);

[0151] FIG. 2 is photographs showing SIJA inter-coat adhesion. (Base coat: DHS BAC70846, C2. Base cure condition: 16 h, 120 F, 8% RH. Over-coat: BAC50103, C. Over-coat cure: 4 days 120 F, 10% RH.);

[0152] FIG. 3 is showing the impact of modifying agent dwell time on over-adhesion performance.

(Base coat: DHS BAC70846, C2. Base cure condition: 16 h 120 F, 8% RH. Over-coat: BAC50103, C. Over-coat cure: 4 days 120 F, 10% RH.);

[0153] FIG. 4 is photographs showing the preliminary stencil interaction results and corresponding SIJA adhesion.

(Base coat: DHS BAC70846, C2. Base cure condition: 16 h, 120 F, 8% RH. Modifying agent dwell time before overcoat ?h. Over-coat: BAC50103, C. Over-coat cure: 4 days, 120 F, 10% RH.);

[0154] FIG. 5 is photographs showing the preliminary stencil interaction results and corresponding SIJA adhesion. (Base coat: DHS BAC70846, C2. Base cure condition: 16 h. 120 F, 8% RH. Modifying agent dwell time before overcoat ?h. Over-coat: BAC50103, C. Over-coat cure: 4 days, 120 F, 10% RH);

[0155] FIG. 6 is photographs showing the preliminary water soak data: 3× applications each of modifying agent system in IPA. (Base coat: DHS BAC70846, C2. Base cure condition: 16 h. 120 F, 8% RH. Over-coat: BAC50103, C. Over-coat cure: 4 days, 120 F, 10% RH.);

[0156] FIG. 7a is a photograph showing SOLO treatment solution application on stencil letter and premask diamond quality (Base coat: DHS BAC70846, C2. Base cure condition: 16 h 120 F, 8% RH. Over-coat: 2 mil DHS BAC50103, C2. Over-coat cure before removal: 16 hr, 120 F.);

[0157] FIG. 7b is a photograph showing Effect of solvent combination on stencil letter clarity employing, base coat (DHS BAC70846, C2 with cure condition: 16 h, 120 F, 8% RH), modifying agent (5 wt % NPZ SOLO with dwell time 1 h), and over-coat (1 mil DHS BAC50103, C with cure condition before removal: 16 hr, ambient);

[0158] FIG. 7c is a photograph showing Image quality employing no modification agent or 5 WT % NPZ employing a 20:80 NPA:Proglyde combination. (Base coat: DHS BAC70846, C. Base cure condition: 3 Cycles of 4 hr, 120 F, 9% RH & 8 hr, 75 F 36% RH. Stencil coat: DHS BAC701 Black, C2.);

[0159] FIG. 8 is photographs showing scribe adhesion.

(Base coat: DHS BAC70846, C2. Cure condition: 16 h, 120 F, 8% RH.);

[0160] FIG. 9 is photographs showing stencil pull & scribe adhesion base coat. (DHS BAC70846, C2. Cure conditions: 16 h, 120 F, 8% RH. Over-coat: DHS BAC50103, C2, 1 mil. Over-coat cure: ambient.);

TABLE-US-00001 Stencil Pull Time (min) Scribe Test Time (h)  5 1 30 2 60 3 90 4

[0161] FIG. 10 is photographs showing SIJA inter-coat adhesion (DHS CA8000 paint); cure conditions as indicated.

[0162] FIG. 11 is photographs showing corresponding WARE results to FIG. 12; cure conditions as indicated.

[0163] FIG. 12 is photographs showing SIJA inter-coat adhesion (DHS CA8800 paint); cure conditions as indicated.

[0164] FIG. 13 is photographs showing SIJA inter-coat adhesion (Eclipse paint); cure conditions as indicated.

[0165] FIG. 14 is photographs showing SIJA inter-coat adhesion (DHS CA8000 paint); cure conditions as indicated.

[0166] FIG. 15 is photographs showing Whirling Arm Rain Erosion data: Modification agent (alkoxide): 5 wt % NPZ in 80% IPA: 20% proglyde;. DHS CA8800:

Basecoat—BAC70846, CTR Thinner,

Overcoat—BAC70281, CTR Thinner.

DHS CA8000:

Basecoat—BAC70846, C Thinner,

Overcoat—BAC707, C Thinner.

Eclipse:

Basecoat—BAC70846, TR109 Thinner,

Overcoat—BAC707, TR109 Thinner.

[0167] Base coat cure conditions as indicated. Overcoat cure
conditions: 4 days at 120 F;

[0168] FIG. 16a is a photograph showing WARE data using DHS CA8800 paint: Basecoat—BAC707 Gray w/varied thinners, Cure conditions: 3 Cycle Cure—4 h, 120 F, 18% RH+8 h, 75 F 70% RH. Overcoat—BAC70846 White w/CTR thinner, Cure conditions: 4 days, 120 F.

[0169] FIG. 16b is a photograph showing WARE data using DHS CA8800 paint: Basecoat—BAC707 Gray w/varied thinners, Cure conditions: 3 Cycle Cure—4 h, 120 F, 18% RH+8 h, 75 F, 70% RH. Overcoat—BAC51265 Blue w/CTR thinner, Cure conditions: 4 days, 120 F;

[0170] FIG. 17a is a photograph showing WARE data: Basecoat—DHS CA8800 BAC70846 White w/CTR thinner, Cure Conditions: 3 Cycles of 4 h, 120 F, 18% RH+8 h, 75 F, 70% RH. Modification agents (alkoxides)—

5Z-60i: 5 wt % NPZ in 60 wt % IPA and 40 wt % proglyde,
5Z-60n: 5 wt % NPZ in 60 wt % NPA and 40 wt % proglyde.
Overcoat—DHS CA8800 BAC70281 Gray w/CTR thinner, Cure conditions: 4 days, 120 F.

[0171] FIG. 17b is a photograph showing WARE data: Basecoat—DHS CA8000 BAC70846 White w/C thinner, Cure conditions: 3 Cycles of 4 h, 120 F, 3% RH+8 h, 75 F, 12% RH.

Modification agents (alkoxides)—
5Z-60i: 5 wt % NPZ in 60 wt % IPA and 40 wt % proglyde,
5Z-60n: 5 wt % NPZ in 60 wt % NPA and 40 wt % proglyde.
Overcoat—DHS CA8000 BAC707 Gray w/C thinner, Cure conditions: 4 days, 120 F;

[0172] FIG. 18a is a photograph showing WARE data: Basecoat—Eclipse BAC70846 White w/TR-109 thinner, Cure conditions: 3 Cycles of 4 h, 120 F, 18% RH+8 h, 75 F, 70% RH. Modification agents (alkoxides)—

5Z-60i: 5 wt % NPZ in 60 wt % IPA and 40 wt % proglyde,
5Z-60n: 5 wt % NPZ in 60 wt % NPA and 40 wt % proglyde.
Overcoat—Eclipse BAC707 Gray w/TR-109 thinner, Cure conditions: 4 days, 120 F;

[0173] FIG. 18b is a photograph showing WARE data: Basecoat-Eclipse BAC70846 White w/TR-109 Thinner, Cure Conditions: LH or HH (See below).

Modification agents (alkoxides)—
5Z-60i: 5 wt % NPZ in 60 wt % IPA and 40 wt % proglyde,
5Z-60n: 5 wt % NPZ in 60 wt % NPA and 40 wt % proglyde.
Overcoat—Eclipse BAC707 Gray w/TR-109 thinner, Cure conditions: 4 days, 120 F. Basecoat Cure LH: 4 h, 120 F, 3% RH+8 h, 75 F, 12% RH for 3 cycles, Basecoat Cure HH: 4 h, 120 F, 18% RH+8 h, 75 F 70% RH for 2 or 3 cycles;

[0174] FIG. 18C is a photograph showing WARE data: Basecoat—Eclipse BAC70846 White w/TR-109 Thinner, Basecoat Cure—LH or HH (See below).

Modification agents (alkoxides)—5Z-60i: 5 wt % NPZ in 60 wt % IPA and 40 wt % proglyde, 5Z-60n: 5 wt % NPZ in 60 wt % NPA and 40 wt % proglyde.
Overcoat—Eclipse BAC707 Gray w/TR-109 thinner, Cure conditions: 4 days, 120 F.
First TC Cure LH: 4 h, 120 F, 3% RH+8 h, 75 F, 12% RH for 3 cycles,
First TC Cure HH: 4 h, 120 F, 18% RH+8 h, 75 F, 70% RH for 2 or 3 cycles;

[0175] FIG. 19

Basecoat—DHS CA8000 BAC70846 White w/C thinner, Cure conditions as indicated.
Modification agents (alkoxides) with 30 minute dwell:
5Z-60n: 5 wt % NPZ in 60 wt % NPA and 40 wt % proglyde,
7Z-60n: 7 wt % NPZ in 60 wt % NPA and 40 wt % proglyde,
9Z-60n: 9 wt % NPZ in 60 wt % NPA and 40 wt % proglyde.
Overcoat cure conditions: 4 days, 120 F.

Overcoats:

[0176] DHS CA8000—BAC5004 Blue w/C thinner, Eclipse-BAC5004 Blue w/TR-109 thinner,
Sky-Hullo FLV-II—900BL004 Blue w/IS-900, Type III thinner;

[0177] FIG. 20 is photographs showing the shelf life of metal alkoxide reactivation treatment solutions on adhesion.

[0178] FIG. 21a is a graph showing soak and recovery experiments using BMSS-142 (polysulfide): Weight change.

[0179] FIG. 21b is a graph showing soak and recovery experiments using BMSS-142 (polysulfide):Volume change.

[0180] FIG. 21c is a graph showing soak and recovery experiments using BMSS-142 (polysulfide):Hardness change.

[0181] FIG. 22a is a graph showing soak and recovery experiments using BMS1-71, CL1 (EPR) elastomer: Weight change.

[0182] FIG. 22b is a graph showing soak and recovery experiments using BMS1-71, CL1 (EPR) elastomer: Volume change.

[0183] FIG. 22c is a graph showing soak and recovery experiments using BMS1-71, CL1 (EPR) elastomer: Hardness change. (0089)

[0184] FIG. 23a is a graph showing soak and recovery experiments using BMS1-71, CL2 (Silicone) elastomer: Weight change.

[0185] FIG. 23b is a graph showing soak and recovery experiments using BMS1-71, CL2 (Silicone) elastomer: Volume change. and

[0186] FIG. 23c is a graph showing soak and recovery experiments using BMS1-71, CL2 (Silicone) elastomer: Hardness change. (0090)

[0187] FIG. 24a is a graph showing soak and recovery experiments using BMS1-57 (Silicone) elastomer: Weight change.

[0188] FIG. 24b is a graph showing soak and recovery experiments using BMS1-57 (Silicone) elastomer: Volume change.

[0189] FIG. 24c is a graph showing soak and recovery experiments using BMS1-57 (Silicone) elastomer: Hardness change.

[0190] FIG. 25 is photographs showing images of elastomers and sealants on recovery;

[0191] FIG. 26 is a graph and photographs showing immersion results for titanium;

[0192] FIG. 27 is a graph and photographs showing immersion results for 2024T3 bare aluminum;

[0193] FIG. 28 is a graph and photographs showing immersion results for 2024T3 clad aluminium;

[0194] FIG. 29 is a graph and photographs showing immersion results for high strength steel;

[0195] FIG. 30 is a graph and photographs showing immersion results for stainless steel.

[0196] FIG. 31a is a photograph showing sandwich corrosion results: 1× magnification.

[0197] FIG. 31b is a photograph showing sandwich corrosion results: 10× magnification.

[0198] FIG. 32 is a graph and photograph showing immersion results for BMS8-79 composite material;

[0199] FIG. 33 is a graph and photograph showing immersion results for BMS8-256 composite material;

[0200] FIG. 34 is a graph and photograph showing immersion results for BMS8-256 with Metlbond;

[0201] FIG. 35 is a graph and photograph showing immersion results for BMS8-276 with SM905 composite material;

[0202] FIG. 36 is a drawing and photographs showing tapeline experiments: Untreated and treated with various modification agent formulations.

[0203] FIG. 37 is a graph showing impact on colour shift for DHS BAC70846 treated with various modification agents & not over-coated following accelerated exposure according to SAE J1960 relative to specimens left untreated and

[0204] FIG. 38 is a diagram of the Lab-SYSTEM.

[0205] FIG. 39 is photographs showing WARE data.

Basecoat—DHS CA8800 BAC900 clear with F thinner, Cure Conditions: 3 heat cycles (4 h, 120 F, 18% RH and 8 h, 75 F, 70% RH).
Modification agent—5% NPZ, 80:20 NPA: Proglyde
Post treatment of Modification agent—none or tack rag
Overcoat—DHS CA8800, white or blue cured for 2 weeks at ambient 72 F, 35% RH.

[0206] FIG. 40 is pencil hardness data for specimens left untreated prior to overcoat or treated with the modification agent prior to over-coating both prior to and following 30 day immersion into hydraulic fluid.

[0207] FIG. 41 is Gardner Impact adhesion test results employing no modification agent or 5 WT % NPZ alkoxide in isopropanol. (Base coat: DHS CA8800 BAC3613 Yellow, CTR thinner. Base cure condition: 3 Cycles of 4 hr, 120 F, 12% RH & 8 hr, 75 F 36% RH. Over-coat: DHS CA8800 various colors, CTR thinner. Overcoat Cure condition: 2 weeks ambient).

EXAMPLES

[0208] The invention will now be described with reference to the following non-limiting examples. Although the examples concentrate on coatings derived from polyurethane chemistries it will be understood that the same activation methodology could be applied to coatings such as but not limited to those based on epoxy, acrylic, polycarbonate, or polyester coatings through the appropriate choice of solvent(s), agent(s) and optional additives under appropriate activation conditions.

[0209] The specific “substrate” the polyurethane topcoat is applied to is not relevant. Hence the substrate can be metal (eg. aluminium), plastic (eg. polyimide), composite (eg. carbon fibre reinforced epoxy or glass reinforced epoxy) or an elastomer (eg. polysulfide elastomer) The substrate may be finished with surfacing materials, films, elastomers or coatings.

[0210] The polyurethane topcoat layer which requires reactivation may have topcoat, intermediate or priming layers beneath it and again these layers are not relevant. Typical examples of build-ups employed in the aerospace industry include: [0211] Aluminium substrate: cleaned, surface prepared with anodize or conversion coat, epoxy based primer(s), optionally selectively strippable intermediate coating layer, and polyurethane topcoat layers. [0212] Epoxy based composite: surface based primer(s), optionally prepared/cleaned, epoxy selectively strippable intermediate coating layer, and polyurethane top-coating layers.

[0213] The reactivation treatment solution is designed in such a way that it can be applied under industrial conditions and the integrity of the “substrate” or coating layers beneath the polyurethane coating which is undergoing reactivation are not adversely effected to a point where they are unsuitable for their intended purpose by interaction of treatment solution which may inadvertently come in contact with it for short periods.

Example 1: Hydrolysis Surface Activation Method

[0214] The example demonstrates that improved SIJA inter-coat adhesion relative to untreated specimens results from activation of the coating prior to over-coating. Inter-coat adhesion provided in this case is similar to specimens reactivated by sanding.

Example 2: Oxidation Surface Activation Method

[0215] The example demonstrates that improved SIJA inter-coat adhesion relative to untreated specimens results from activation of the coating prior to over-coating. Inter-coat adhesion provided in this case is similar to specimens reactivated by sanding.

Example 3 Reduction Surface Activation Method

[0216] The example demonstrates that improved SIJA inter-coat adhesion relative to untreated specimens results from activation of the coating prior to over-coating. Inter-coat adhesion in this case is similar to specimens reactivated by provided sanding.

Example 4: Light Induced Photo-Grafting Surface Activation Method

[0217] The example demonstrates that improved SIJA inter-coat adhesion relative to untreated specimens results from activation of the coating prior to over-coating. Inter-coat adhesion provided in this case is similar to specimens reactivated by sanding.

Example 5: Reduction Surface Activation Method

[0218] The example demonstrates that improved Scribe green adhesion (predictor of possible problems during masking tape removal) relative to untreated specimens results from activation of the coating prior to over-coating. Inter-coat adhesion provided in this case is similar to specimens reactivated by sanding.

Example 6: Reduction Surface Activation Method

[0219] Stripping study indicated that coatings reactivated by surface reduction methods strip quicker than specimens sanded prior to over-coating but slower than coatings over-coated without treatment.

Example 7 and 8 Evidence of Surface Chemistry Change

[0220] Results indicate that a higher Specific contribution to surface energy results (γsP), particularly to surfaces activated with the reduction strategy.

Examples 9 to 33 Reduction Surface Activation Method

Examples 34 and 5: Surface Activation Method with Exchange Agents

[0221] It is envisaged that suitable combinations of components of the activation treatment will differ depending on the type of coating to be activated. The appropriate choice of solvent(s), agent(s), optional additives and inerts, and activation conditions will differ depending on the type of coating to be activated.

General Experimental Detail

Painting Conditions and Protocol

[0222] Spray painting of many flat panels was carried out employing a Yamaha robotic painting arm incorporating a gravity fed Binks Mach lA automatic spray gun configured with a 94 nozzle. Spray painting was conducted using an inlet pressure of 40 PSI, a scan rate of 100 mm/s and a specimen to gun distance of 300 mm. The coating thickness was controlled by the gun's fluid needle control position and scan rates. These parameters were adjusted in line with paint thickness measurements and assessed using a Fischer Isoscope (MPOD) on aluminium substrates. When coating was completed on composite substrates, the coating layer thickness was estimated by calibration with the isoscope readings from aluminium panels. An analogous strategy was employed for the application of the primers, optional intermediary and topcoat layers. For the majority of the examples, the painted films were over-coated following taping through the middle of the coupon with 3M vinyl tape (#471) to form a paint edge on its removal. This edge was the impact target for SIJA (Single Impact Jet Apparatus) analysis.

[0223] Spray painting of curved or larger surfaces (eg: rain erosion foils) and some of the smaller flat panels was typically conducted using a Binks Ml-H HVLP gun configured with a 94 nozzle. Occasionally, a similar gravity fed HVLP gun or a pressure pot fed HVLP gun was used. In these cases the aluminium or composite was prepared in the same manner as the flat plates prior to the first top-coat being applied. Following cure of the first coating layer the front of the foils were masked (Intertape Polymer Group, PG-777 tape) prior toover-coating to form a leading edge once the over-coating was applied and tape removed.

[0224] Cure protocols were undertaken in a computer controlled temperature humidity chamber, such as a Thermoline Environmental chamber and/or a conventional curing oven.

Table 1 Paint Material Information

[0225] For the majority of the examples, the coatings used are listed in Table 1. In the examples, paint companies are generally abbreviated:

PRC-DeSoto International: PRC-DeSoto

Akzo-Nobel Aerospace Coatings: Akzo-Nobel

[0226]

TABLE-US-00002 TABLE 1 Intermediate Primer Coat Topcoat Coating Epoxy based Intermediate PRC-DeSoto primers suitable coat that International: for composite or is selectively Desothane aluminium based strippable HS, aerospace Akzo-Nobel Aerospace componenets Coatings: Eclipse, Deft Chemical Coating Components Base: CA8000/BxxxxxX such as CA8000/B70846X Activator: CA8000B Thinner 1: CA8000C Thinner 3: CA8000C2 Or Base: CA8800/Byyyy Activator: CA8800Z Thinner 1: CA8800CTR Thinner 2: CA8800CT Thinner 3: CA8800CT2, Base: ECL-G-xxxx such as ECL-G-14 (BAC70846) Curing Sol: PC-233 Thinner TR-109 Thinner TR-112; Sky-Hullo FLV-II Base: 900YYxxx such as 900BL004 (Blue) Curing Sol: 900X001CAT Thinner: IS-900, TyIII Note: the thinner designation C and C2 are used to indicate the relative rate at which the paint cures. C thinners - standard cure rate with C2 producing a correspondingly faster cure rate (from incorporation of high catalyst levels into the thinner). For Desothane CA8800 CTR is reduced rate, CT is standard rate and CT2 is fast rate cure thinner. For Akzo-Nobel fast cure thinner is designated TR-112 and standard thinner TR-109.

Painting Conditions and Protocol

[0227] Substrates were cleaned prior to priming and optionally where appropriate treated with an alodine type conversion coating or anodized.

[0228] Polyurethane topcoats, intermediate and primer layers were mixed and applied according to the paint manufacture instructions. Primer:

[0229] Typical conditions: [0230] For Composite or aluminium: application of common aerospace epoxy based primer optionally incorporating additives to aide corrosion resistance at 0.5 mil (12.5 micron) dry film thickness (dft) per manufacturer instructions.
Intermediate coat: [0231] Optionally application of intermediate coat (IC) that is selectively strippable at 0.35 mils (10 microns) according to manufacturer instructions

[0232] Polyurethane topcoat: [0233] Application of polyurethane topcoat (eg: Desothane HS topcoat containing CA8000/B70846X base (white color of this topcoat also designated as BAC70846. In examples it is typically designated as Desothane HS 70846X or DHS BAC70846) at 1.0 to 4.0 mil (typically 1.0 mil (25 micron)). Painted panels flash off for 1 hour prior to cure and accelerated aging.

[0234] Standard cure I accelerated aging conditions Employed for topcoats were: (i) Cure painted panels in oven at 120° F., 5-10% RH (Relative Humidity) for 40 hours, followed by (ii) post cure in a humidity chamber at 120° F. (49° C.) and 50% RH for 48 hours, and then (iii) oven cure at 160° F. for 24 hours. Total cure time was 112 hours. Alternatively other “accelerated” aging protocols were employed as specified in the examples to render the polyurethane topcoat unreceptive to additional coating layers as indicated by poor adhesion under standard adhesion tests eg: 120° F. and 2-3% RH for 5 days or 120° F. and 5% RH for 16 hours or as specified in the examples.

Surface Modification

[0235] The solvents and agents used for surface modification were purchased from the MERK and Sigma-Aldrich or Dow Chemical Companies. Purity was of an Analytical or Laboratory Reagent grade purity. Isopropanol and n-propanol were generally of an anhydrous grade. However, alternative suppliers and grades of the reagents are known to be available.

TABLE-US-00003 TABLE 2 General Activation Protocol Task Strategy Treatment Spray application of the reactivation treatment solution employed a Binks Ml-H HVLP gun with a 92 or 94 nozzle and 20 psi inlet pressure or, on occasion, a similar HVLP gravity or pressure fed gun or by a flood application where indicated. The active agent (eg: reducing agent such as LiBH.sub.4) was dissolved, dispersed or suspended in the solvent/s at a percentage based on weight and the hence prepared ″reactivation treatment″ applied to the substrate for a given period Post- Spray on leave on application (SOLO) Treatment Optionally the polyurethane surface may be ″post″ treated Washed with water (or solvent) a period following treatment - spray on-hose off (SOHO) or Wiped with an isopropanol, ketone (eg: methyl-propyl ketone) or water soaked cloth - spray on wipe off (SOWO) Re- Samples were over-coated with polyurethane topcoat either: coating Same day (5 mins to 4 hours after treatment) Some period following reactivation. Unless otherwise specified for SIJA or rain erosion adhesion testing, overcoat thickness was 100 micron employing Eclipse or Desothl(lf HS coatings cured with standard thinners. Cure conditions were 120 F. under 8-20% RH for at least 48 hours unless specified. Scribe test overcoat paint thickness was typically 25 to 50 microns

Analysis

[0236] Table 3 provides the equipment and conditions used for testing for analytical purposes.

TABLE-US-00004 TABLE 3 Testing Equipment & Conditions Equipment Conditions SIJA Adhesion testing was completed using a Single Impact Jet Apparatus (SIJA, Cambridge). The initial equipment was typically configured using a 0.8 mm nozzle typically and employed 0.22 calibre 5.5 mm Crosman Accupell Pointed Pellets (#11246). Testing was completed following immersion in water for 16 to 18 hours, employing a line laser to locate the impact position, and using a 45° specimen to impact droplet geometry. A single water jet was employed at each site to test adhesion with the pressure employed for the ″shot″ indicated below its impact. The velocity of each individual shot was recorded for futurere f eren ce, but generally the pressure to velocity conversion is specified be low (±25 m/s). Pressure (PSI) Velocity (m/s) L 350  50 610 100 725 200 895 Alternatively the impa ct was dictated by a ″dot″ or via the velocity employed eg. 600 m/s. In some cases the amount of overcoat removed, and hence the inter-coat adhesion was assessed employing image an alys is techniques to quantify the area of paint removed. However regardless of the impact velocity relative to the unmodified reference more overcoat removed corresponded with inferior inter-coat adhesion. Scribe Scribe adhesion was assessed according to (BOEING Adhesion Specification Standard) BS S7225, Class 5. This adhesion test is a five line cross-hatch tape (3M tape, No .250) pulltest. Briefly: Heat aged polyurethane coatings were reactivated and then over-coated (25-80 micron thickness) curing the over-coat for 16 hours at room temperature and 50% RH. The coatings were then scribed according to BS S7225 (Cl5 scribe cross-hatch) and the adhesion test performed. The paint adhesion of specimens are rated on a scale of 10 to 1 with ″10 ″ being no paint removed and ″1″ being all paint removed. Whirling Rain erosion testing was completed on a whirling arm Arm Rain rain erosion apparatus employing a 52 inch zero lift helicopter like propeller run at 3600 rpm. Reference and activated polyurethane topcoat foils were over- coated (85 to 120 micron paint thickness) following masking to produce a leading edge. The foils were attached to the propeller at a distance along the propeller correlating to a velocity of 380 mile per hour at the mid point of the foil. The effective rain field density of 2 mm droplets used during the experiment was 1 inch per hour. After 30 min the impact of rain erosion on the inter-coat adhesion of the foils was evaluated according to a 0.5 to 5 rating correlating with the amount of paint removed or tear length. The impact of water droplets on the leading edge of the over-coat formed on removal of the tape during the experiment erodes the over-coating layer relative to the strength of the inter-coat adhesion. (F or Fail or red markings indicate less than acceptable adhesion) Paint Procedure for the complete strip test is described in SAE Stripping MA4872, Annex A, pages 51 to 53. In this Stage an abbreviated version was completed using benzyl alcohol based paint strippers without thermal cycling to compare how the activated and over-coated specimens to untreated and reference specimens. Aged specimens (Aluminium or composite substrate) were untreated, sanded, or activated, were over-coated (60- 75 micron), and cured for40 hours at 120° F. The edges were taped with Aluminium tape (such as 3M Scotch Brand No, 425) prior to commencing the test. Stripper was applied every 2 hours until the coating was removed. Lifting paint was removed just prior to reapplication of the stripper using a plastic squeegee. Contact Contact angle analysis was completed using ″FIRST TEN Angle ANGSTROMS″ semi-automated video equipped contact angle analyser. CH.sub.2I.sub.2 and H.sub.20 were employed as the reference solvents to calculate the dispersive (γs.sup.d) and polar (γs.sup.p) contributions to surface energy (γs) through the Young-Dupre FTIR FTIR analysis was carried out on a BRUKER FTIR/NIR spectrometer or Nicolet Instruments, employing NaCl plates or an ATR KRS-5 TiBr/TiI mixed crystal associated with the microscope. Extent of surface contamination was assessed by swabbing the surface with a ″Q-tip″ soaked with hexane. Following evaporation of the hexane solution onto NaCl, powder NaCl plates suitable for FTIR analysis were prepared by compression moulding. SEM SEM analysis of the polyurethane cross-sections were collected on a Oxford Pentafet detector controlled by an Oxford ISIS system. Cross-sections of the samples, prepared with a cut off saw appropriate for non-ferrous materials, were mounted in epoxy resin, ground and polished to a 1 micron finish and gold coated. Imaging and x-ray analysis was conducted using a 15 KV accelerating voltage and a 17 mm working distance. EDX analysis was specifically refined for carbon, nitrogen, oxygen, and chlorine. Hydrogen Activity of reducing agent was determined by employing Evolution Hydrogen Evolution techniques. The activity of the reducing agent solution (eg. LiBH4 in Proglyde DMM) was determined by measuring the quantity of hydrogen evolved following interaction with dilute aqueous acid. Accelerated Equipment: Atlas (Xenon Arc) Weatherometer UV Outer filter = borosilicate Inner filter = quartz exposure Light intensity: 0.55 W/m 2/nm @340 nm Operation Cycle (SAE J1960): Panels: Desothane HS 70846 White Test for: Colour shift of previously reactivated (but not over- coated) panels Reactivation potential of samples conditioned through aging protocol then a UV cycle. Hydraulic Specimens were tested for coating pencil hardness fluid prior to immersion into the fluid and rated in exposure hardness according to the following protocol (soft to hard). After 30 days immersion the specimens were re-tested. Values reported are the softest pencil that would cut into the paint surface. Hardness Scale (Soft to Hard) 6B 5B 4B 3B 2B B HB F H 2H 3H 4H 5H 6H Gardner Both sides of the test specimen were subject to Impact varying impact forces in 10 inch pound increments Adhesion using a Gardner 160 inch pound capacity impact testing machine with a 0.625 inch diameter hemispherical indenter. Values reported are the highest force recorded that produced no cracking of paint in either the forward or reverse impact Maximum impact tested was 80 inch pounds.

Example 1: Hydrolysis Method

[0237] SIJA inter-coat adhesion of Desothane HS 70846X white (30±5 μm, CA8000C thinner) cured 40 hour at 120° F. (9% RH) followed by 48 hour at 120° F. (50% RH) followed by 24 hour at 160° F., activated and over-coated with Desothane HS S601X blue (104±10 μm).

[0238] Activation Treatment: 30 min, horizontal application position (IPA wipe post treatment)

Example 2: Oxidation Method

[0239] SIJA inter-coat adhesion of Desothane HS 70846X white (30±5 μm, CA8000C2 thinner) cured 40 hour at 120° F. (9% RH), followed by 48 hour at 120° F. (50% RH) and 24 hour at 160° F., activated and over-coated with Desothane HS S601X blue (104±10 μm).

[0240] Activation treatment time 30 min, (IPA wipe post treatment)

Example 3: Reduction Method

[0241] SIJA inter-coat adhesion of Desothane HS 70846X white (30±5 μm CA8000C2 thinner) cured 40 hour at 120° F. (5% RH) followed by 48 hour at 120° F. (50% RH) and 24 hour at 160° F., activated and over-coated with Desothane HS S601X blue (104±10 μm).

[0242] Treatment 30 min, (SOHO—post treatment).

Example 4: Light Grafting Method

[0243] SIJA inter-coat adhesion of Desothane HS 70846X white (30±5 μm, CA8000C-thinner) cured 40 hour at 120° F., (9% RH), followed by 48 hour at 120° F., 50% RH and hour at 160° F., activated 120 min, wiped (IPA) and over-coated with Desothane HS S601X blue (104±10 μm).

[0244] Initiator System: Camphorquinone (1% w/w based on acrylate), Dimethyltoluidine (120% w/w based on camphorquinone) system placed under an 2×18W fluorescent desk lamp.

Example 5: Reduction Surface Activation Method—Green Scribe Adhesion

[0245] Green (scribe) inter-coat adhesion of Desothane HS 70846X white (30±5 μm CA8000C2 thinner) cured 40 hour at 120° F. (9% RH), followed by 48 hour at 120° F. (50% RH) and 24 hour at 160° F., activated and over-coated with Desothane HS S601X blue (68±10 μm, 16 h ambient cure). Green adhesion rating as per BSS7225.

Example 6 Reduction Activation Method—Stripping Rate Test

[0246] A—Untreated, B—Sanded, C—Treatment with 2% NaBH.sub.4 in ethanol, 30 min

Example 7 Evidence of Surface Energy Change

Surface Energy Results for Activated Surfaces Employing a Thermally Aged Desothane HS 70846X Substrate (CA8000C Thinner)

[0247]

TABLE-US-00005 Surface Energy Contact Angle (mJ/m2) (°) Specific Dispersive Treatment Conditions Water CH2I2 γs.sup.p γs.sup.d C Thinner Fresh 76.5 39.0 4.2 42.0 Aged Untreated 76.2 40.3 4.5 41.3 Aged IPA Wipe 75.8 35.0 4.0 44.0 Aged - 2% EtOH/EtOH 37.0 36.6 23.7 43.2 Sodium wash Aged - 1% EtOAc/IPA 69.7 29.4 5.8 46.6 Acetic Acid wipe Aged- 2 × 18 W 65.2 43.5 8.5 43.5 Camphorquinone fluorescent (1% w/w based desk lamp, on acrylate), MAK wipe Dimethyltoluidine (120% w/w based on Camphorquinone) methylamylketone
Fresh—4 hour at 120° F. (approx. 9% RH)
Aged—40 hour at 120° F. (approx. 9% RH), 48 hour at 120° F. (50% RH) and 24 hour at 160° F.

Example 8: Evidence of Surface Energy Change

[0248] Surface energy results for activated surfaces employing a thermally aged Desothane HS 70846 substrate (C2 thinner)

TABLE-US-00006 Surface Energy Contact (mJ/m2) Angle (°) Specific Dispersive Treatment Conditions Water CH2I2 γs.sup.p γs.sup.d C2 Thinner Fresh 71.4 27.6 5.0 47.3 Aged Untreated 74.6 45.5 5.7 38.5 Aged IPA Wipe 73.9 36.3 4.9 43.4 Aged - 2% EtOH/ 42.6 32.2 19.7 45.3 Sodium EtOH Borohydride wash Aged - 1% EtOAc/ 67.9 28.7 6.5 46.9 Acetic Acid IPA wipe Aged - 2 × 18 W 68.6 27.3 6.0 47.4 Camphorquinone fluorescent (1% w/w based desk lamp, on acrylate), MAK wipe Dimethyltoluidine (120% w/w based on Camphorquinone) Fresh - 4 hour at 120° F. (approx. 9% RH) Aged - 40 hour at 120° F. (approx. 9% RH), 48 hour at 120° F. (50% RH) and 24 hour at 160 ° F.

Example 9

[0249] SIJA inter-coat adhesion of aged Desothane HS 70846X white (C2) reactivated under the conditions specified for 30 min (SOHO) and over-coated with Desothane S400X red 3 hours following hose-off with water.

[0250] Treatment Solutions Prepared in Progylde (Dipropylene Glycoldimethyl Ether).

[0251] Results indicated that improved inter-coat adhesion is possible employing “mild” reducing agents such as NaBH.sub.4 and LiBH.sub.4.

Example 10

[0252] SIJA inter-coat adhesion of aged Desothane HS 70846X white (C2) reactivated under the conditions specified for 30 min(SOHO) and over-coated with Desothane HS S601X blue 3 hours following hose-off with water.

[0253] Treatment solutions prepared in dipropylene glycol dimethyl ether at 0.2% concentration. Results indicate that reducing agents with different strengths may be employed for the purpose of reactivation.

Example 11

[0254] SIJA inter-coat adhesion of aged Desothane HS 70846X white (C2) reactivated under the conditions specified for 30 min (SOHO) and over-coated with Desothane S400X red 3 hours following hose-off with water.

[0255] Treatment solutions prepared in dipropylene glycol dimethyl ether.

[0256] Example illustrates that a variety of different concentrations may be employed to “activate” the surface of polyurethane based coatings towards over-coating to provide improved adhesion.

Example 12

[0257] (i) SIJA Inter-Coat Adhesion of Aged Desothane HS 70846X

white (C2) reactivated under the conditions specified (SOLO) for 3 h and over-coated with Desothane HS 5070X blue.

[0258] Treatment solutions prepared in dipropylene glycol dimethyl ether.

[0259] Example illustrates that very low concentrations of the reducing agent may be employed to “activate” the surface of polyurethane based coatings towards over-coating using a spray on leave on approach.

(ii) Scribe adhesion of aged Desothane HS 70846X white reactivated under the conditions specified and over-coated with Desothane HS 5070X blue. The overcoat was allowed to cure under ambient conditions for 16 h prior to conducting the test

[0260] The example illustrates that excellent scribe adhesion results are possible employing low concentrations of reducing reagent under various application conditions.

Example 13

[0261] (i) SIJA Inter-Coat Adhesion of Aged Eclipse BAC70846 White Reactivated Under the Conditions Specified (SOLO) for 3 h and Over-Coated with Desothane HS 5070X Blue.

[0262] Treatment solutions prepared in Progylde (dipropylene glycol dimethyl ether) using LiBH.sub.4 as the reducing agent.

[0263] Example illustrates that a variety of different reducing agent concentrations may be employed to “activate” the surface of polyurethane based coatings towards over-coating from different manufacturers and polyurethane chemistries.

(ii) Scribe adhesion of aged Eclipse BAC70846 white reactivated under the conditions specified and over-coated with Desothane HS 5070X blue. The overcoat was allowed to cure under ambient conditions for 16 h prior to conducting the test

[0264] The example illustrates that improved scribe adhesion results were possible employing low concentrations of reducing reagent to reactivate different types of polyurethane topcoats under various application conditions.

Example 14

[0265] SIJA inter-coat adhesion of aged Desothane HS70846X white reactivated with LiBH4 (0.2 wt %) in the solvent/s specified (SOLO) for 3 h and over-coated with various coloured Desothane HS polyurethane topcoats.

[0266] Results indicate that different solvents may be employed for reactivation using reducing agents under appropriate conditions.

Example 15

[0267] (i) SIJA Inter-Coat Adhesion of Aged Desothane HS 70846X White Reactivated with LiBH4 (0.2 wt %) in Proglyde DMM and Co-Solvent Specified (SOLO) for 3 Hours and Over-Coated with Various Coloured Desothane HS Polyurethane Topcoats.
(ii) Example incorporating different alcohols (40%) and alcohol combinations (20:200).

[0268] Results indicate that under appropriate conditions a variety of solvent combinations may be employed for the purpose of reactivation with appropriate reducing agents.

Example 16

[0269] SIJA inter-coat adhesion of aged Desothane HS 70846X white (C2) reactivated under the conditions specified for 30 min(SOHO) and over-coated with Desothane S400X red 3 hours following hose-off with water.

[0270] 1.0% Li (OCH3)xBH4-x in Proglyde prepared by addition of 0 (x=O), 1 (x=1, major component)), 2 (x=2, major component), and 3 (x=3, major component) equivalents (Eq) respectively of methanol “in-situ”.

[0271] Example illustrates that the active agent may be prepared “in situ” and that reactivation can be conducted in the presence of more than one different type of reducing reagent.

Example 17

[0272] SIJA inter-coat adhesion of aged Desothane HS 70846X white (C2) reactivated under the conditions specified for 30 min (SOHO) and over-coated with Desothane S400X red 3 hours following hose off with water.

[0273] Example illustrates that different treatment solution preparation methods can be employed to manufacture the reduction based reactivations formulation taking into consideration the different ways in which reducing agents are packaged and sold commercially. In certain circumstances the reactive agent may be generated “in situ” if required.

Example 18

[0274] Rain erosion adhesion results for Desothane HS 70846X white (C2) aged as specified. Reactivated using the formulations and treatment time specified before over-coated with Desothane HS 50103X blue. [0275] (i) Ageing protocol: 4 h (120F, 2-3% RH). SOLO based reactivation method [0276] (ii) Ageing protocol: 5 Days (120F, 2-3% RH) SOLO based reactivation treatment [0277] (iii) Ageing protocol: 4 h (120F, 2-3% RH) SOHO based reactivation method [0278] (iv) Ageing protocol: 5 days (120F, 2-3% RH) SOHO based reactivation method

[0279] Results illustrate that improved inter-coat adhesion is possible using reducing agents mixed into various reactivation treatment formulations and applied under various treatment times and protocols for substrates aged under various protocols.

Example 19

[0280] Rain erosion adhesion results for aged Desothane HS 70846X white (C-thinner) applied onto epoxy-carbon fibre composite incorporating primer, intermediate and topcoat layers reactivated under the conditions specified before being over-coated with Desothane HS S601X blue.

[0281] Example illustrates that reactivation of aged polyurethane topcoats can be completed using the reducing methodology on “composite substrates” incorporating paint lay-ups including selectively strippable intermediate coating layers beneath the polyurethane topcoat.

[0282] Note: sanded and untreated reference in duplicate, chemically reactivated in triplicate.

Example 20

[0283] SIJA inter-coat adhesion of aged Desothane HS 70846X white (C2) reactivated with LiBH.sub.4 (0.2 wt % in Proglyde DMM) for 2 h under the post treatment conditions specified before being over-coated with Desothane HS S601X blue.

[0284] Example illustrates that various “post treatment” protocols may be employed depending on the application I process requirements without negatively impacting adhesion.

Example 21

[0285] SIJA inter-coat adhesion of aged Desothane HS 70846X white (C2) reactivated with LiBH.sub.4 (0.1 wt % in Proglyde DMM) multiple times 30 min apart under the conditions specified before being over-coated with Desothane HS S601X blue.

[0286] Example illustrates that multiple applications of the reactivation treatment solution does not diminish adhesion performance.

Example 22

[0287] SIJA inter-coat adhesion of aged Desothane HS70846X white (C2) reactivated with LiBH.sub.4 (0.1 wt % in ProglydeDMM) for (i) one hour before being subjected to the conditions specified and then washed (water) allowed to dry or (ii) for the treatment time specified before being over-coated with Desothane HS S601X blue or S400X red.

[0288] The example demonstrates that reactivation can be conducted for a short (5 min) or extended period (8 days) and that the reactivated surface retains its reactivity towards subsequent paint layers under a variety of conditions.

Example 23

[0289] SIJA inter-coat adhesion of aged Desothane HS 7084X6 white (C2) reactivated with LiBH.sub.4 solutions themselves previously aged under ambient conditions for the period specified before being over-coated with Desothane HS S601X blue.

(i) Treatment solutions: 0.2% LiBH.sub.4 in Progylde DM+the percentage IPA indicated stored for 50 days before being used to reactivate the aged polyurethane topcoat.
(ii) Treatment solutions: Various LiBH.sub.4 concentrations stored in Proglyde DMM/20 tBAC for 90 days prior to application
(iii) Treatment solution: LiBH.sub.4 prepared as a stock 0.5 wt % concentration in Proglyde DMM and stored for 6 months. Dilutions to the indicated concentrations and formulations were made just prior to application of the treatment solution for the purpose of reactivation in a SOLO format
(iv) Rain erosion adhesion data from Desothane HS 70846X white (C) cured at 120F (10% RH) 4 days prior to reactivation and over-coating with Desothane HS S601X blue. NOTE: Reactivated samples in triplicate, benchmark untreated and sanded in duplicate.
Treatment solutions (a) Aged for 25 days (b) Aged for 25 days
(c) Stock solution in Proglyde DMM aged for 25 days and IPA added just prior to application to provide the given concentration (d) prepared fresh (e) prepared fresh.

[0290] Examples illustrate that reactivation treatment solutions stored under ambient conditions retain their activity thus providing shelf life and pot-life robustness.

Example 24

[0291] Example demonstrates that application of the treatment solution can assist in the mitigation of common surface contaminants (residues), produced by the manufacturing assembly which can reduce both the visual appearance and inter-coat adhesion particularly when the reactivation treatment solution is applied as a SOHO or SOWO application technique.

(i) Illustration of application of common surface contaminates to the surface of an aged Desothane HS 70846X white topcoat prior to reactivation and over-coating with Desothane HS 5070X blue.
Corresponding SIJA inter-coat adhesion results from contaminant quadrants
(ii) SIJA inter-coat adhesion of aged Desothane HS white 70846X topcoat contaminated with (a) petroleum jelly or (b) Aeroshell 33 prior to reactivation employing 0.1% LiBH4 in Proglyde DMM I 20 tBAC. Activation treatment left on for (30 minutes) prior to application of the designated post treatment conditions specified. Subsequently over-coated with Desothane HS S601X blue.
(a) Petroleum jelly contaminant

(b) Aeroshell 33

[0292] The above example clearly demonstrates that improved inter-coat adhesion and paint appearance may be obtained when the Desothane HS coatings contaminated with common aerospace residues from manufacturing processes are reactivated prior to over-coating.

(iii) Supporting FTIR evidence for selected contaminants: Samples were swabbed with a hexane soaked “Q-tip” and the hexane containing sample absorbed onto NaCl. Following compression molding of the NaCl into Plaques, FTIR spectra was obtained.

(a) Petroleum Jelly Contaminant

[0293] NOTE: typical absorptions around 3000 cm-.sup.1 for the contaminant was removed or reduced following reactivation under the conditions listed.

(b) Aeroshell 33 Contaminant

[0294] NOTE: typical absorptions around 3000 cm-1 for contaminant was removed or reduced following reactivation under the conditions listed.

[0295] Examples illustrate that the level of contaminate is clearly reduced or removed following the reactivation treatment.

(iv) Supporting surface energy results for selected contaminants following no treatment, solvent wipe only and reactivation treatments of the contaminated aged Desothane HS 70846X white topcoat under the conditions specified.

TABLE-US-00007 Surface Energy (mJ/m.sup.2) 0.1% LiBH4 (Proglyde, 2% MEK/MPK tBAc) MEK/ No Treatment Wipe Only MPK Wipe Dis- Dis- Dis- Contamination persive Specific persive Specific persive Specific None 45 4.2 43 3.9 45 8.6 Microcut 48 3.2 45 4.2 45 6.9 Catoil 47 2.0 44 2.9 45 6.0 Boelube 37 6.0 46 3.5 46 5.9 Aeroshell 33 43 2.2 44 2.8 46 8.0 Petroleum 49 3.0 41 3.9 43 6.5 Jelly

[0296] The specific surface energy component of total surface energy is significantly reduced after contaminants are applied to the surface of the aged Desothane HS 70846X substrate. Wiping the surface with just solvent only marginally improved the specific contribution to surface energy (not back to untreated, non-contaminated) whilst specimens reactivated with LiBH4 under the conditions listed provided a significant improvement in the specific contribution to surface energy above that for non-contaminated substrates indicating simultaneous cleaning and reactivation has occurred.

Example 25

[0297] (i) Example 25. (i) SIJA inter-coat adhesion of aged Desothane HS 70846X white (C2) reactivated under the conditions specified—one (thin application) or two (thicker application) applications followed by water hose-off after the 30 minute treatment time (SOHO) and over-coated with Desothane S400X. Following cure of the over-coating the samples were immersed in Skydrol aviation fluid for a period of 30 days under ambient conditions prior to adhesion testing.

[0298] The example illustrates that the inter-coat adhesion between topcoat layers is resistant to hydraulic fluids.

(ii) SIJA inter-coat adhesion of aged Desothane HS 70846X white reactivated under the conditions specified (SOLO, 180 min) and over-coated with Desothane HS S601X blue. Following cure of the over-coating the samples were immersed in water under ambient conditions or placed in a condensing humidity chamber at 120F/98% RH for a period of 30 days prior to adhesion testing and visual appearance assessment.

[0299] Results indicate that excellent inter-coat adhesion was obtained after 30 days water soak under ambient conditions or 30 days conditioning at 120F and 95% RH. Paint appearance is also acceptable and further improved by either using sediment (precipitate free) treatment solutions obtained from filtering, or post treatment protocols such as a tack rag wipe, wash (SOHO) or wipe (SOWO) processes.

Example 26

[0300] (i) The following example illustrates effects of spray application of 0.1% LiBH.sub.4 [0301] Proglyde DMM reactivation solution onto bare polysulfide based sealant (PRC-Desoto PR1772) that has been applied over primed carbon fiber reinforced epoxy.

[0302] Example illustrates that no lifting, bubbling of the sealant occurs even at thin sealant thicknesses.

[0303] Adhesion of the sealant to the substrate is maintained even through application of rubbing.

[0304] (ii) The following example illustrates scribe adhesion results from polysulfide sealant (PRC-Desoto PR 1772) cured for 4 h before treatment with a reactivation treatment solution comprised of 0.1% LiBH.sub.4 in proglyde for the time specified before overcoating with Desothane HS S601X Blue and curing for 16 h under ambient conditions.

[0305] The example illustrates that no deleterious effects occur following application of the treatment solution onto the sealant prior to over-coating even when the treatment solution is applied onto only moderately cured (young) sealants.

[0306] (iii) The following example provide weight change data for polysulfide sealant (PRC-Desoto PR 1772) when immersed into different solvents and reactivation treatment solutions.

[0307] (iv) The following example illustrates what impact application of LiBH.sub.4 I proglyde reactivation solutions has on selective strippable (intermediate) coating layers applied over primed composite panels.

[0308] The example demonstrates that no lifting or dissolution of the intermediate coating layer occurs through interaction of the reactivation treatment solution.

[0309] (v) The following examples provide immersion weight change data up to 28 days of various aerospace substrate materials in various solvents, typical aerospace paint stripper, and reactivation treatment solutions. (a) BMSS-256—carbon fiber reinforced epoxy (b) BMS8-79—glass fiber reinforced epoxy (c) BMS8-276—carbon fiber reinforced epoxy with Metlborid 1515 adhesive film (d) BMS 8-276 with Surface Master 905 adhesive film (e) Various metals, Al-aluminum, Ti—titanium, SS—stainless steel, HSS—high strength steel.

[0310] The examples demonstrate that the reactivation solutions may be formulated for minimal negative interaction with a range of materials from plastics, composites, elastomers, and metals relative to common solvents or chemical formulations often used in industries such as the aerospace sector. In the case of metals, weight loss is within measurement uncertainty

Example 27

[0311] The following examples demonstrate the reactivation solution may be used in conjunction with materials such as stencils and design masks and tapes for the production of decorative painted finishes.

[0312] (i) Reactivation (LiBH4 in proglyde:IPA 40:60 SOLO application 30 min) applied onto aged Desothane HS white 70846X topcoat (16 h, 120F, 8% RH) with pre-applied vinyl based stencil prior to painting with Desothane HS S601X blue (C2) cured for 16 h at ambient conditions.

[0313] (ii) Reactivation (LiBH.sub.4 in proglyde:IPA 40:60 SOLO application 30 min) applied onto aged Desothane HS white 70846X topcoat (16 h, 120F, 8% RH) with pre-applied vinyl based stencil prior to painting with Desothane HS S601X (C) blue at 120F for 16 h.

[0314] Example illustrates that crisp non-distorted designs are maintained even when the treatment solution is applied over the top of the mask.

[0315] (iii) Reactivation (0.15% LiBH4 in proglyde:IPA, 30 min, SOLO) applied onto aged Desothane HS white 70846X topcoat (16 h, 120F) with pre-applied vinyl based stencil prior to painting with Desothane HS S601X blue (C2).

[0316] Example illustrates that excellent green adhesion, verified by scribe and stencil pull tests, is possible after 1 h with reactivated samples unlike untreated and excellent letter clarity is possible across a range of stencil pull times.

Example 28

[0317] Desothane HS 3613X yellow or S400X red (C2) cured aged under the standard aging protocol was reactivated using the LiBH.sub.4 concentrations indicated for 30 min SOLO prior to overcoating with Desothane HS S601X blue.

[0318] The example illustrates that different coloured polyurethane coating may be reactivated using the reduction strategy.

Example 29

[0319] (i) SEM pictures of Desothane HS 70846X white polyurethane coatings both (C) and (C2) aged under the (a) standard cure cycle aging conditions and (b) low humidity conditions (120F, 5 days, 2-3% RH) prior to and following reactivation with 0.1% LiBH4 in proglyde.

[0320] Example a illustrates that the surface of the coating looks similar prior to and following reactivation. Example b illustrates that the surface of the coating looks similar prior to and following reactivation

[0321] (ii) Surface energy results for Desothane HS 70846X white polyurethane coatings both (C) and (C2) aged using the (a) standard cure conditions and (b) low humidity cure conditions (120F, 5 days, 2-3% RH) prior to and following reactivation with 0.1% LiBH4 in proglyde

TABLE-US-00008 Substrate Surface Energy (mJ/m.sup.2) Cure Treatment* Dispersive Specific Low Humidity Cycle (5 days, 120 F., 2-3% RH) ″C″ — 44.2 5.4 ′C″ 0.1% LiBH.sub.4 43.9 6.3 ″C2″ — 41.5 5.5 ″C2″ 0.1% LiBH.sub.4 42.4 7.3 Ageing Cycle: 120° F., 5% RH 40 h, (ii) 120° F. 50% RH 48 h, and (iii) oven cure at 160° F. for 24 h ″C″ 43.6 3.6 ″C″ 0.1% LiBH.sub.4 45.4 5.9 ″C2″ 45.2 4.2 ″C2″ 0.1% LiBH.sub.4 45.5 7.3

[0322] Example illustrates that increases in the Specific contribution to surface energy results from exposure to the reactivation treatment solution for the coatings aged under difference conditions and with catalyst levels (eg: C and C2).

(iii) FTIR-ATR results from Desothane HS 70846X white polyurethane coatings (C2) aged under the standard conditions and reactivated as indicated.
(iv) SEM cross section images of cured aged Desothane HS 70846X white (C2) applied over primer and aluminium substrate (a) untreated, (b) sanded and (c) reactivated using 0.1% LiBH4 in proglyde 30 min SOLO prior to over-coating with Desothane HS S601X blue.

[0323] Examples illustrate that the over-coat does not wet the aged Desothane coating when untreated providing de-bonded regions. The de-bonded regions are not present in the sanded and. chemically reativated samples, providing evidence for improved interfacial interaction between the two polyurethane topcoat coating layers (white and blue).

Example 30

[0324] Example illustrates the impact of accelerated UV exposure on aged Desothane HS 70846X polyurethane coating relative to untreated reference for different lengths of exposure time.

(i) Change in colour for samples not over-coated

[0325] The example illustrates that the colour shift is similar for samples untreated, sanded, reactivated with 0.1% LiBH4 in proglyde that is either removed after 30 min (SOHO) or not removed (SOLO) if left not over-coated prior to various lengths of accelerated UV exposure time.

(ii) SIJA inter-coat adhesion results for Desothane HS 70846X white (C2) aged under the standard protocol and then accelerated UV conditions for 630 h before reactivation and over-coating with Desothane S601X.

[0326] The example illustrates that the reactivation protocol provides improved inter-coat adhesion for samples exposed to accelerated aging and UV exposure with similar result provided to those samples not exposed to UV.

[0327] This example is relevant to polyurethane coating that has undergone UV exposure for extended periods before requiring reactivation and over-coating, for example, in-service airplanes.

Example 31

[0328] Example shows a comparative paint stripping experiment between composite panels incorporating a primer, intermediate and polyurethane topcoat layers. In the example the stripping behaviour of aged Desothane HS 70846X white (C2) reactivated with the reduction method under the conditions listed prior to over-coating with Desothane HS S601X relative to untreated and sanded references.

[0329] The example illustrates that the chemically reactivated samples, strip in a similar time frame to the sanded and untreated references.

t=initial
Top row (from left to right): 17, 18, 19, 20
Bottom row (left to right): 21, 22, 23, 24

17—Untreated

18—Sanded

[0330] 19, 20—0.05% Lithium Borohydride t-Butyl Acetate: Proglyde 2:98 (SOHO)
21, 22—0.01% Lithium Borohydride t-Butyl Acetate: Proglyde 2:98 (SOHO)
23, 24—0.05% Lithium Borohydride t-Butyl Acetate: Proglyde 2:98 (SOHO)

[0331] The example illustrates that the chemically reactivated samples strip in a similar time frame to the sanded and untreated references.

Example 32

[0332] The following example shows the impact on paint adhesion and appearance of Desothane HS S601X applied over untreated and reactivated aged Desothane HS 70846X coatings (themselves applied over primed aluminum) under cycling temperature and humidity for 500 cycles.

[0333] (i) Scribe adhesion was rated “10” for all samples

[0334] (ii) SIJA adhesion testing provided improved inter-coat adhesion similar to sanded following the cycling protocol.

[0335] (iii) No change of paint finish was noted in terms of “micro-cracking” or “pin head defect formation” following the cycling

[0336] The examples illustrate that no apparent reduction in adhesion or over-coat appearance occurs following cycling of temperature and humidity.

Example 33

[0337] Example demonstrates the paint adhesion and overcoat paint quality of rain erosion foils following simulation of typical paint masking hangar operations and heat cure. The examples show rain erosion foils, (incorporating primer, intermediate coating, and) topcoated with Desothane HS CA8000/B70846X base with C thinner cured/aged for 5 days at 3% RH and 120° F. which were reactivated for 1.5 hours using SOHO (prior to wash off) or the SOLO process indicated.

[0338] Following reactivation the samples either underwent a 6 hour 120F thermal cycle directly (then left under ambient conditions overnight) or alternatively prior to the thermal treatment were wrapped with Kraft paper or had 4 bands of masking tape perpendicularly wrapped around the samples. After removal of the paper and tape (wiping the tape lines with IPA) the samples were painted with Desothane HS CA8000/B50103 base with C thinner and following cure tested for adhesion and paint appearance relative to unreactivated and sanded controls.

[0339] (i) SOHO Reactivation

[0340] (ii) SOLO Reactivation

[0341] Results indicate: [0342] All the foils except for a random SOLO foil passed with good marks [0343] Excellent paint appearance was noted: No ghosting seen from the tape being on the foil that was cured for 6 hours and then being solvent wiped with IPA and no deleterious effects from application of Kraft paper were noted [0344] No significant difference from a 1 application situation and a 3 application situation

Example 34

[0345] The following example illustrates the inter-coat adhesion of aged Desothane 70846X and S400X red untreated and reactivated with tetraisopropyl titanate or sanded reference prior to over-coating with S601X blue and 5070X light blue.

(i) SIJA Adhesion

[0346] The example illustrates that treatment of the aged surface with tetraisopropyl titanate provides improved adhesion with different coloured aged polyurethane substrates and over-coatings.

(ii) The following example demonstrate the reactivation solution based on tetraisopropyl titanate may be used in conjunction with materials such as stencils and design masks and tapes for the production of decorative painted finishes.

[0347] Untreated Reference

[0348] 5% Tetraisopropyl Titanate in IPA

[0349] The example illustrates that the use of the treatment solution based on tetraisopropyl titanate applied as a treatment solution for aged Desothane HS 70846X prior to over-coating with Desothane HS 5070X improved adhesion compared with the untreated reference and also provided minimal letter swelling or figure distortion, when it is applied SOLO directly over the design stencil prior to over-coating with polyurethane.

Example 35

[0350] Screening experiments assessed a variety of metal alkoxide modifying agents with different relative reactivities (moisture stabilities) as described in Table 4.

[0351] Initial experiments employed SIJA methods to probe the change in inter-coat adhesion with (i) the type of metal alkoxide used in the activation treatment system and (ii) its concentration. Under all conditions a SOLO approach was employed. FIG. 1 provides the SIJA data employing 0.5, 3 and 5 wt % concentrations of modifying agent. It should be pointed out that (i) there was no true concentration parity in the experiment although given the large concentration range investigated trends in performance could be assessed and (ii) all solutions were prepared in the one solvent system (IPA) to simplify the experiment even though it is known that alcoholysis is possible to provide mixed alkoxides. However, to counter this effect to some degree each solution was prepared freshly and applied directly. Considering that NPZ has a high molecular weight and was supplied as a 70% NPA solution the actual concentration was much lower than for similar titanium based reagents.

[0352] Metal alkoxides with small alkoxy groups (eg: TPT, NBT, NPZ see Table 4) appeared to provide limited benefit at concentrations of 0.5 wt % but under the reactivation conditions employed showed improved inter-coat adhesion at concentrations above 3 wt %. A lower reactivity for TEAZ was observed probably due to its greater moisture stability (Table 4). Closer investigation of concentration (FIG. 2) indicated that around 6-7 mmol of modifying agents per 100 g was required to see paint removal comparable to sanded specimens with less paint removed as the concentration was increased.

[0353] A preliminary investigation was also undertaken to assess the activity of the substrate over time considering that along with a standard reactivation time (eg 30 to 60 minutes) there may also be a requirement in the paint hangar for the activated surface to remain active after a heat cycle or for shorter or longer periods. Preliminary assessment results are provided in FIG. 3. The salient points from this study were that (i) NPZ treatment solutions appear to build up adhesive forces faster than TPT, (ii) both versions provided about the same level of intercoat adhesion after 1 h even though the respective molar concentration of NPZ was less, (iii) paint surfaces remain active after 24 h at ambient conditions, and (iv) the surfaces remained active after a heat cycle. Point (i) may be explained by the relative reactivity of the materials as provided by their difference in hydrolysis rate (Table 4). This type of activation window was considered commercially attractive and appeared to provide some flexibility for paint hangar scheduling.

TABLE-US-00009 TABLE 4 Properties Of Various Metal Alkoxides Promoter/ Tetra-i- Tetra-n-propyl Tetra-n- Property propyltitanate titanate butyltitanate Formula Ti(O-i-C.sub.3H.sub.7).sub.4 Ti(O-n-C.sub.3H.sub.7).sub.4 Ti(O-n-C.sub.4H.sub.9).sub.4 MW 284 284 340 Abbreviation TPT NPT NBT Supply 100% 100% 100% Density 0.965 1.05 1.0 (g/mL   Pour Point +17 (Melt Point) −50 <−70 (° C.) Flash point   23-60 38 50 Relative 0.5-2.0 0.5-2.0 1.0-2.5 hydrolysis rate (mL     Relative moles 3.5 3.5 2.9 at 1 wt in 100   Formula Zr(O-n-C.sub.3H.sub.7).sub.4 Zr(C.sub.6H.sub.14NO.sub.3).sub.4 Zr(O-n-C.sub.3H.sub.7).sub.4 MW 327 683 327 Abbreviation NPZ TEAZ NPZ Supply 70% (NPA) 100% 70% (NPA) Density 1.07 1.34 1.07 (g/mL   Pour Point −70 — −70 (° C.) Flash point 21-25 >100 21-25 (° C.) Relative 0.02 >500 0.02 hydrolysis rate (g/mL   Relative moles 3.5 3.5 2.9 at 1 wt % in 100 g indicates data missing or illegible when filed

TABLE-US-00010 TABLE 5 Physical Properties of Various Solvents Boiling Vapor point* pressure Flash Point Solvent/Material (QC) (mmHg @ 20° C.) (° C.) Isopropanol (IPA) 82 33 12 n-Propanol (NPA) 97 14.9 22 n-Butanol (NBA) 116 4.5 35 Hexanol 156 0.5 59 Ethylhexanol 184 0.36 73 Dipropylene glycol 175 0.6 65 dimethylether (Proglyde DMM) Methyl ethylketone 80 71 −1 (MEK) Methyl propylketone 101 27 7 (MPK) *start of boiling point range provided

[0354] Based on the results provided for LiBH4 based modifying agents stencil and pre-mask swelling appeared to be more related to the physical properties of the solvent system employed rather than the low concentrations of the active agent. To confirm this with metal alkoxide modifying agents a brief study was undertaken with the results provided in FIGS. 4 and 5. As was shown for LiBH.sub.4 treatments in 100% Proglyde DMM extensively swelled the vinyl mask whilst 100% IPA provided no swelling. Since slight swelling began at a ratio of approximately 60:40 IPA: proglyde this ratio was considered a reasonable upper limit for the amount of glycol ether in formulations to be used with stencils. The effect of modifying agent concentration for NPZ in NPA or TPT in IPA was also undertaken (FIG. 5) with the results confirming that in 100% alcohol at least the concentration range (0.5 to 5.0 wt %) did not appear to negatively impact letter quality.

[0355] Preliminary 30 day water soak experiments were also undertaken with specimens reactivated and then over-coated. One to three applications of the modifying agent were investigated to simulate both thin and thick applications, over spray, multiple passes etc. Generally good over-coat appearance was observed even with high concentrations of TPT or NPZ (5 wt %) at 1 to 3 applications (FIG. 6).

Pre-Mask and Stencil Vinyl Swelling

[0356] Based on the preliminary results for stencil swelling, full stencil and premask diamond studies were undertaken. Using 100% IPA or NPA in the solvent system did not appear to provide appreciable stencil or pre-mask swelling and as such letter clarity was crisp even when the reactivation solution was applied over vinyl mask materials SOLO (FIG. 7a) Following encouraging whirling arm rain erosion results (see later) additional stencil swelling experiments were undertaken employing 5 wt % NPZ in a range of solvents and combinations (FIG. 7b). No negative impact was demonstrated by using a 20:80 ratio of proglyde DMM to IPA or NPA, although at a 40:60 ratio some slight wicking away from the edges of the stencil was noted. Considering the benefits provided by using a slightly higher proglyde concentration in terms of adhesion on thicker paint layers, this degree of stencil swelling may be acceptable and probably not observed on pre-mask vinyl considering its lower susceptibility to swelling or when applied for short dwell times (15 min). Alternatively, different solvent formulations can be employed depending on whether the application is for stencils which typically uses paint layer thickness on the order of one mil or premask or large body area applications where the paint layer thickness is typically two to five mils.

[0357] Tests using a 5 wt % NPZ are provided in FIG. 7C. It should be pointed out that using difficult to remove Chinese characters letter quality was significantly improved compared to untreated specimens and there was no appearance of stencil swelling when a 5% NPZ 20:80 proglyde:IPA solvent system was employed for reactivation.

Adhesion

[0358] Leveraging the preliminary results provided in the initial screening experiments above, the majority of subsequent experiments were completed employing a 3 wt % concentration of modifying agent in alcohol based solvents. Later, higher concentrations of modifying agent and the addition of proglyde to the solvent system was found necessary to provide acceptable whirling arm rain erosion results on thick layers of paint in certain circumstances. It should also be emphasised that as indicated in FIG. 2, concentration parity was not maintained between TPT and NPZ with a 3 wt % solution actually corresponding to a 10.5 and a 6.6 mmol/100 g concentration respectively.

Scribe Adhesion

[0359] Various scribe adhesion test results are provided in

[0360] FIG. 8. Although the 3.5 h, 120F cure stencil results did not provide a reference material that failed BSS7225 (and as such it was not possible to discriminate between the reactivation treatments) the 12 h ambient cure overcoats did with the reactivated samples providing a “10” rating similar to sanded for in contract to untreated with a “0” rating.

[0361] Stencil pull and scribe adhesion were also undertaken (FIG. 9) and mirror that completed for LiBH.sub.4. Regardless of the treatment dwell (30 or 90 min), the treatments provided excellent scribe results (10 in BSS 7225) after 60 min under ambient conditions superior to that of both sanded (8) and untreated (3). In terms of stencil pull: pull times of 90 min (more severe) did provide a “thinner” letter for all the reactivations treatments. Results for TPT were somewhat superior to NPZ regardless of whether IPA or NPA was employed which might be attributed to the difference in effective concentration. However, stencil pull results were on the whole far better than untreated with effectively a full letter present at a stencil pull time of 60 min (similar to sanded specimens) whereas untreated specimens only provided a full letter at a pull time of 30 min.

[0362] SIJA and Rain Erosion Adhesion

[0363] Based on those strategies WARE foils were prepared with the main aim of (i) obtaining concentration parity between TPT and NPZ, (ii) employing Desothane CA8000 base coat cured with standard “C” thinner, (iii) exploring the potential for using proglyde as a co-solvent, and (iv) probing the effect of multiple applications. In all the experiments a relatively long application time was employed (4 h) to provide a sufficient time frame for the metal alkoxide to firstly react and then condense with the aged paint surface. Subsequent tests demonstrated that much shorter dwell (application) times, e. g. 30 minutes, were feasible.

[0364] The results from SIJA panels are provided in FIG. 10 and the WARE results obtained from foils provided in FIG. 11. Although reasonable paint removal was obtained for the untreated reference from the 16 h, 120F heat cycle cure (at 8% RH or 0.59 wt % air moisture), the 72 hr basecoat ambient cure (at 60% RH or 1.12 wt % air moisture) provided an untreated reference with only marginal paint loss. As such it was again difficult to compare the relative performance of the reactivation treatments. Table 6 provides tabular data for the WARE results given in FIG. 11. All foils produced “passes” with the “C” cured base coating under the 16 h, 120F, 8% RH cure. For the ambient cured foils, all the NPZ foils had superior WARE compared to the TPT foils. Fot the TPT foils, multiple applications appeared to help, although incorporation of 20% proglyde provided the greatest advantage with ⅔ foils passing the test (eg a marginal pass). The reason for this is complex: (i) the addition of proglyde assists in spraying a more uniform treatment film, (ii) proglyde has a much lower vapour pressure than IPA or NPA and as such the surface remained “wet” somewhat longer which presumably also assisted in promoting surface chemical reactions, (iii) proglyde is known to soften the paint and as such probably promoted metal alkoxide penetration into the coating surface and hence chemical reactions with embedded chemical groups, and (iv) through that process favors the formation of a surface/subsurface interpenetrating network during condensation of the alkoxide prior to or during cure of the over-coat.

TABLE-US-00011 TABLE 6 WARE results for FIG. 11 OHS BAC70846 Base coat: 16 h, 120 F., 8% RH, C2, Adhesion promoter 2 h dwell, Overcoat BAC50103, 96 h 120 F., C2 3% TPT 3% TPT in 3% TPT i IPA PG:IPA, 5% NPZ 5% NPZ Untreated Sanded in IPA x2 1:4 in IPA in NPA 0.5 4.3 4.8 4.6 4.4 4.6 4.5 0.  4.9 4.5 4.8 4.8 4.0 4.6 4.9 4.8 4.0 4.6 4.7 0.4 4.6 4.7 4.7 4.4 4.4 4.6 OHS BAC70846 Base coat: 72 h, 75 F., 60% RH, C2, Adhesion promoter 2 h dwell, Overcoat BAC707, 96 h 120 F., C2 3% TPT 3% TPT in 3% TPT in IPA PG: IPA, 5% NP 5% NPZ Untreated Sanded in IPA x2 1:4 in IPA in NPA 2.0 4.9 2.0 2.4 4.1 4.8 4.8 2.4 4.9 2.3 3.5 3.7 4.5 4.9 2.3 3.3 4.0 4.9 4.9 2.2 4.9 2.2 3.1 3.9 4.7 4.9

[0365] The findings from the trials with Desothane CA8000 on metal alkoxides may be summarised generally as follows: [0366] (i) NPZ is preferred over TPT [0367] (ii) NPA is preferred over IPA [0368] (iii) Small amounts of proglyde co-solvent appear to be helpful [0369] (iv) For maximum benefit, metal alkoxide concentrations should be >10 mmol/100 g [0370] (v) Multiple application provide a more limited benefit [0371] (vi) Reactivation of high humidity cured specimens appeared to be more complex compared with low humidity cure (surface chem. related/moisture present in coating etc.

[0372] Based on those findings a SIJA screening experiment was completed with Desothane CA8800 and Eclipse coatings employing the same two cure scenarios albeit that the ambient cure relative humidity was increased to 80% RH (1.56 wt % air moisture). The results are provided in FIGS. 12 and 13. Reactivation employing either TPT or NPZ using a variety of solvent systems provided improved levels of inter-coat adhesion under both cure conditions. The extent of improvement was such that further discrimination between the alkoxides and solvent systems employed was difficult to assess, although introduction of proglyde into the formulation as an 80:20 blend did appear to further enhance the performance. Further SIJA screening was also completed on Desothane CA8000 using 5 wt % NPZ and several proglyde to n-propanol and isopropanol solvent ratios as shown in FIG. 14. Results using 5 wt % NPZ in a solvent solution of proglyde and either IPA or NPA with 30 to 60 minute dwell time of the modifying agent prior to overcoat paint are provided in FIGS. 15 to 18. FIG. 15 shows the rain erosion results employing a 20:80 proglyde:IPA solution for different dwell times and for “high” humidity (1.31 wt % air moisture) and “low” humidity (0.22 wt % air moisture) cure scenarios. In all cases the modifying agent treatment provided excellent inter-coat adhesion to both Desothane CA8000 and CA8800 coatings with just the high humidity cure Eclipse providing failures. FIG. 16a explores the effect of Desothane CA8800 cure rates using reduced rate (CTR), standard rate (CT), and fast rate (CT2) cured overcoats and a CTR cured base coat employing the same reactivation treatment. For BAC70846 white over BAC707 gray good passes were obtained for the CTR and CT thinners. The faster CT2 cured over-coat did not provide so good a performance (⅔ foils rated above 4) although it should also be noted that sanded also failed under similar conditions. When BAC51265 Blue was used as the overcoat (CTR) and the BAC 707 gray base coat cured with the different thinners (FIG. 16b), high passes were obtained for each of the cure rates. This suggests that reactivation of the basecoat is relatively insensitive to the cure rate (thinner) employed in the basecoat. FIGS. 17a and b documents the effect of higher proglyde concentrations (40%) and the impact of NPA or IPA as the alcohol in the 5 wt % NPZ formulation using difficult to over-coat systems including Desothane CA8800 gray on white cured under high humidity and CA8000 cured under low humidity conditions. In both cases excellent passes were obtained with little differentiation between the two types of alcohols employed.

[0373] Given those results the treatments were applied to high humidity cured Eclipse base coats which had been previously shown to fail when exposed to 5 wt % NPZ in 80:20 IPA:proglyde (FIG. 18a) In the case of formulations employing 60% IPA no passes were obtained when three cycles of the humidity protocol were used even when two application and longer adhesion promoter dwell times were employed although specimens cured at low humidity were successfully reactivated (FIG. 18b). Two cycles of the high humidity protocol, however, did provide good passes. In contrast the 60% NPA formulation provided passes with three cycles of the humidity cure protocol with ⅔ foils passing after only 1x 30 min application and with 2×30 or 60 min treatment solution applications 3/3 foils passed the adhesion test (FIG. 18c). From these results, NPA performed slightly better than IPA for intercoat adhesion. This difference in NPZ formulations could be due to (i) longer dwell time re: vapour pressure or (ii) mixed alkoxides from the inter action of IPA in the solvent system not favouring reactivation of such materials. Intuitively one might predict that steric hindrance would be greater in the mixed alkoxide system which could reduce the reaction rate with the substrate surface or ability for it to interpenetrate into the coating.

[0374] To determine if higher concentrations of modifying agent would show even further improvements in WARE, NPZ formulations up to 9 wt % (19.8 mmol/lOO g) with a solvent of 60 wt % NPA/40 wt % proglyde were tested using CA8000 basecoat cured at 120F under low (3% RH, 0.22 wt % air moisture) and moderately high humidity (13% RH, 0.95 wt % air moisture) conditions for eight days. Various paintlines CA8000 (FIG. 19A), Eclipse (FIG. 19B), and Sky-Hullo (FIG. 19C) were used as overcoats. All foils (18/18) passed using 5 wt % NPZ, 13/18 foils passed using 7 wt %, and only 10/18 passed using 9 wt %. The Sky-Hullo over coat was particularly discriminating with 6/6 foils passing using 5 wt %, 4/6 using 7 wt %, and 1/6 using 9 wt %. Overall, the results in FIGS. 19A to 19C suggested that the optimum NPZ concentration is near 5 wt % and the optimum alkoxide concentration is near 0.11 mmol per gram.

[0375] Preliminary shelf life SIJA data is provided in Figure and suggested that the modifying agent was not negatively affected by storage under ambient conditions. After three months all of the solutions (stored in glass) were precipitate free indicating a low level of hydrolysis and hence polymerisation. Although the solutions were prepared in either NPA or IPA it was not anticipated that the addition of 20 to 40% proglyde would negatively impact storage stability, particularly since proglyde can be obtained essentially moisture free. Other storage containers such as high density polyethylene could be used. The modifying solution could also be stored as a two part kit, similar to how many aerospace paints are packaged, where one part would contain the NPZ either at wt % or at diluted concentration and the second part would contain aproglyde/alcohol solvent solution.

Sealant & Elastomer Interaction

[0376] Sealant and elastomer immersion results are provided in FIGS. 21 to 24. In those tests BMS5-142 sealant was immersed in modifying agent solutions with IPA or NPA as the solvent for a period of 24 h, whilst elastomers were immersed for 7 days and the change in weight, volume and hardness monitored both during the immersion as well as on recovery relative to MPK and water reference solutions. FIG. 25 provides images of the sample following recovery and illustrates that the samples were not obviously eroded or negatively impacted visually. Considering that MPK has solubility parameters of [dispersion, polar, and H-bonding] [16.0, 9.0 and 4.7 J/cm.sup.3], NPA [16.0, 6.8 and 17.4 J/cm.sup.3] and employing the rule of mixtures a 40:60 blend of ProglydelNPA [15.6, 5.0 and 12.0 J/cm3], the proglydelNPA solvent blend should not provide a substantial interaction with these types of materials.

[0377] In the case of BMS5-142 (polysulfide non-chromate sealant) weight gain reported in FIG. 21A was more significant for MPK relative to the reactivation treatment solutions and correspondingly the volume change in FIG. 21B was also greater. This result indicated a relatively low interaction between the treatments and the polysulfide sealant. After 7 days recovery all modifying agent treatment solution immersed samples were within 5% of their initial pre-treatment hardness, whilst both the water and MPK immersed samples were less than 10% softer.

[0378] BMSl-71, CLl (EPR) elastomers provided the greatest weight gain in MPK and material appeared to be extracted by the reference solutions. Weight loss on recovery in MPK was about 12% after 7 days compared to less than 4% for samples immersed in the treatments. Correspondingly shrinkage on recovery was greater for the MPK reference, whilst the 7 day recovery Shore hardness at 17% increase was slightly higher than the 9 to 12% increase for samples immersed in TPT or NPZ. Similar results in FIG. 23 were provided by BMSl-71, CL2 (Silicone). During immersion, that material also showed a great uptake of MPK after 7 days (70% weight increase) compared to the treatment and water solutions (15%), but weight and volume (<5%) and hardness changes (<10%) were all similar during recovery. BMSl-57 (Silicone) was also less susceptible to treatment solution uptake than MPK (20% weight gain re: 90%). Weight and volume loss during recovery were less than 10% (typically <5%) for all immersions, and presumably was caused by material extraction during immersion. Hardness increase for the treatment solutions upon recovery was about 20%, whilst for MPK it was 10%. The larger hardness increase could indicate a larger sensitivity of this elastomer to the treatment solutions than to MPK, a commonly used cleaning component. However, the treatment solutions are typically sprayed on as thin films rather than flooded or wiped on as is typical for cleaning solutions so the 7 day soak of the treatment solutions is an extreme condition.

[0379] Metal Interaction

[0380] Commonly used aerospace metals were also investigated for weight change and visual appearance following 30 day immersion in the metal alkoxide solutions compared with water (FIGS. 26 to 30). As a general point weight loss or gain was very low (not much more than the resolution of the 4 decimal place balance) and generally much less than water which appeared for most substrates to be the most aggressive. Weight gain for titanium was less than 0.07% for the treatment solutions re:0.14% for water although samples in the reactivation solution did appear to be more “tarnished”. This colour shift was reversed for 2024-T3 aluminium with water providing significant discolouration and weight change of 1.2% compared with less then 0.1% for the treatments. 2024-T3 clad samples accumulated a dull finish following immersion in water and less weight gain compared with the bare Al at just 0.8% increase. However treatment solution samples produced less than a 0.05 wt % increase. Weight gains for high strength and stainless steel immersed in treatment solutions were all less than 0.02 wt % and similar to or less than for water. Interestingly NPZ in IPA did not appear to tarnish high strength steel the way the other systems (inc. water) did although this observation did not translate into a significant difference in weight gain. Sandwich corrosion was tested according to ASTM Fl 110 with the results provided in FIG. 31. Without magnification both the reference water and treatment solutions appear to provide surface discolouration with outpitting to most of the surface.

Composite Interaction

[0381] Immersion results provided in FIGS. 32 for to 35 several relative composite systems are to MPK and CEEBEE paint stripper. Samples were cut and immersed without any edge taping and as such, considering the small sample size, represented a most severe immersion test since the cut edges are regions for easy treatment penetration for example through pores/fibre-matrix de-bonding from the cutting process and more generally from the effective “cut” surface to volume ratio. As general comments (i) the CEEBEE paint stripper appeared to be the most aggressive towards all systems resulting in weight gains in the 1.5 to 4% range after a month immersion (ii) generally immersion in the treatment solution also led to weight gain rather than loss (apart from BMS 8-276 with SM905), although in such cases the weight change was generally very low (less than 0.5% for all composites and about 0.1% for BMS 8-276 with SM 905. In several instances initial weight gain was larger (eg 24 hr 7 days) with this reducing after longer periods of immersion which may be possible if some material was extracted from the system over time or broke off.

Interaction with Tapes

[0382] Preliminary tape interaction studies are provided in FIG. 36 and were considered of critical importance to application of the modifying agent technology for decorative painting of air craft. In this experiment the effect of tape line, tape ghosting, and IPA wipe to remove residue were evaluated. In general no more paint wicking was observed for samples reactivated prior to/following taping with generally crisp lines present regardless of the modifying agent formulation applied. With TPT a larger amount of modifying agent residue was expected considering its effective concentration at 5 wt % was larger than the NPZ examples (17.5 mmol/lOO g re:11 mmol/lOO g). However no appreciable ghosting effects were obvious meaning that even a 1 mil overcoat thickness was sufficient to hide the tape lines.

Interaction with Coatings

[0383] During production there remains the potential for paints to be reactivated (eg through over-spray) but not over-coated. Considering that the process of reactivation modifies the surface of the paint, there remains the potential for some accelerated aging brought about via environmental factors such as heat, water and UV irradiation. To assess this, coupons painted with a white basecoat were subjected to accelerated aging according to SAEJ1960 protocols employing a weatherometer. FIG. 37 provides the change in colour (delta E) over time for coupons treated with modifying agent, sanded, or untreated relative to an untreated, painted coupon stored in the dark and measured at each time increment. Both untreated and sanded, UV exposed samples showed colour shift values in the range of one delta E unit during the experiment. As expected treated coupons at zero time show some colour shift compared the untreated coupon at zero time. Samples reactivated with titanium were slightly lighter and had a yellow/green colour shift prior to exposure. On exposure residue treatment not well bonded to the surface would be anticipated to be removed (washed away) due to the SAE J1960 protocol. This can account for the rapid change in delta E after the equivalent of three months exposure. However, in both 3/6 month cases the samples were shifted darker and after an initial drop in the yellow shift became more yellow at 6 months.

[0384] Generally speaking colour shifts for Zr based modifying agents were less than the Ti based one. With increasing exposure leading naturally to a slight darkening and yellowing of the coating not dissimilar in magnitude to untreated samples.

Further Performance

[0385] Further application of the modification agent is provided in FIGS. 39 to 41. FIG. 39 provides WARE results for clear coated samples (eg paints without pigment) either treated or non-treated prior to over-coating as well as the implication of the effects of any post-treatment process such as wiping with a tack rag prior to over-coating. In all cases the specimens treated with the modification agent provided superior inter-coat adhesion and on some occasions superior to sanded.

[0386] FIG. 40 provides hardness measurements prior to and following immersion in hydraulic fluid. The results indicated that the adhesion promoting mechanism is compatible with hydraulic fluid with pencil hardness values either approximately the same as or harder than specimens left untreated prior to over-coating thus providing another benefit.

[0387] FIG. 41 provides Gardner impact test results for treated and untreated specimens of various paint thickness. The test is used for predicting the ability of organic coatings to resist cracking or peeling caused by impacts producing rapid deformation of the underlying (metal) substrate). The results show that the modifying agent does not increase the brittleness of the paint and could possibly reinforce the some paint combinations at lower thickness.

[0388] It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.